1. Field of the Invention
The present invention relates to a scramble system for use in a television broadcast signal transmitted in the form of a scrambled signal.
2. Description of the Related Art
In television broadcasting, there is now commercially available a scrambled broadcasting by which only particular reception contract viewer is permitted to enjoy a video program. In this scrambled broadcasting, as a television broadcast signal transmitted from a broadcasting station, for example, there is used a signal that is scrambled such that a normal picture cannot be reproduced by an ordinary television receiver. Then, a decoding apparatus for descrambling the scrambled broadcasting wave is distributed to only contractors who pay charges according to a predetermined method. The viewer can then enjoy normal picture and sound by connecting the decoding apparatus to the receiving apparatus.
However, in the pay channel television broadcasting carried out by the scrambled broadcasting system, it is frequently observed that a video program is illegally enjoyed by the viewer by abusing the decoding apparatus. In the ordinary pay channel broadcasting, the contractor is permitted to view only the received television broadcasting by the television receiver or only to record such television broadcasting by a viewer's VTR. Accordingly, it is illegal that a video tape in which the received television broadcasting is recorded is distributed or a television broadcasting is received outside the contracted service area. Further, it is also illegal that the television broadcasting is viewed at a place where many people can watch television broadcasting such as a hotel or the like although the viewer made the contract for only personal use in the home.
According to the conventional scrambled broadcasting, if the decoding apparatus is so effective, then it is impossible to avoid the illegal viewer. For example, even when a pirated video tape in which the scrambled broadcasting is descrambled recorded is distributed in the market, it is impossible to specify the decoding apparatus from such pirated video tape.